Concrete Calculator Concrete Network

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Concrete Calculator

Slab / Rectangular Footing Circular Column / Post Hole

Results

Cubic Yards:
Cubic Feet:
80lb Bags:
60lb Bags:

*Note: A 10% waste factor is recommended to be added to these totals to account for spillage or uneven subgrade.

Understanding Concrete Estimating

Estimating concrete accurately is critical for both DIY projects like patios and professional construction jobs. Ordering too little concrete leads to "cold joints" and structural weaknesses, while ordering too much is a waste of money and material.

How to Calculate Cubic Yards

Concrete is typically sold by the cubic yard. To calculate the volume for a standard slab, you use the following formula:

  1. Convert all measurements to feet (Inches divided by 12).
  2. Multiply Length × Width × Thickness = Total Cubic Feet.
  3. Divide Total Cubic Feet by 27 = Total Cubic Yards.

Using Bags vs. Ready-Mix

For small projects, buying bags of concrete mix from a home center is cost-effective. For larger slabs, ordering a ready-mix truck is more efficient. Here are standard yields for premixed bags:

  • 80lb Bag: Yields approximately 0.60 cubic feet. You need about 45 bags to make 1 cubic yard.
  • 60lb Bag: Yields approximately 0.45 cubic feet. You need about 60 bags to make 1 cubic yard.

Calculation Example

If you are pouring a patio that is 10 feet long, 10 feet wide, and 4 inches thick (0.33 feet):

10 × 10 × 0.33 = 33 cubic feet.
33 / 27 = 1.23 cubic yards.

If you were using 80lb bags: 33 / 0.60 = 55 bags.

function toggleInputs() { var type = document.getElementById('shapeType').value; var rectDiv = document.getElementById('rect-inputs'); var circDiv = document.getElementById('circ-inputs'); if (type === 'slab') { rectDiv.style.display = 'block'; circDiv.style.display = 'none'; } else { rectDiv.style.display = 'none'; circDiv.style.display = 'block'; } } function calculateConcrete() { var type = document.getElementById('shapeType').value; var unitCost = parseFloat(document.getElementById('unitCost').value) || 0; var cubicFeet = 0; if (type === 'slab') { var length = parseFloat(document.getElementById('lengthFt').value); var width = parseFloat(document.getElementById('widthFt').value); var thickness = parseFloat(document.getElementById('thicknessIn').value); if (isNaN(length) || isNaN(width) || isNaN(thickness)) { alert("Please enter valid numbers for length, width, and thickness."); return; } cubicFeet = length * width * (thickness / 12); } else { var diameter = parseFloat(document.getElementById('diameterIn').value); var depth = parseFloat(document.getElementById('depthFt').value); if (isNaN(diameter) || isNaN(depth)) { alert("Please enter valid numbers for diameter and depth."); return; } var radius = (diameter / 12) / 2; cubicFeet = Math.PI * Math.pow(radius, 2) * depth; } var cubicYards = cubicFeet / 27; var bags80 = cubicFeet / 0.60; var bags60 = cubicFeet / 0.45; document.getElementById('resYards').innerText = cubicYards.toFixed(2) + " yd³"; document.getElementById('resFeet').innerText = cubicFeet.toFixed(2) + " ft³"; document.getElementById('res80lb').innerText = Math.ceil(bags80); document.getElementById('res60lb').innerText = Math.ceil(bags60); var costDisplay = document.getElementById('costResultContainer'); if (unitCost > 0) { var totalCost = cubicYards * unitCost; costDisplay.innerHTML = "Estimated Material Cost: $" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); } else { costDisplay.innerHTML = ""; } document.getElementById('concrete-results').style.display = 'block'; }

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